The invention relates to a magnetic bearing having a fixed first bearing portion and a movable second bearing portion which is contactlessly supported on the first bearing portion.
Magnetic bearings are e.g. employed for supporting motor rotors, pump rotors or other rotating parts, but also for supporting non-rotating parts, e.g. they may be used as damping and cushioning device between two non-rotating parts. A magnetic bearing generally comprises a fixed first bearing portion with a magnetic coil generating a magnetic field which is canalized by a yoke, and a second movable bearing portion. The second bearing portion comprises a permanent magnet of which magnetization is in alignment with the yoke. Depending on the direction of the magnetic field generated by the magnetic coil of the first bearing portion, the permanent magnet of the second bearing portion is either attracted or repelled such that the first bearing portion can generate both attracting and repelling forces acting upon the second bearing portion. It is a drawback of this configuration that the permanent magnet of the second bearing portion has an attracting effect upon the yoke of the first bearing portion such that always considerable attraction forces occur. Said attraction forces represent a biasing force which must be counteracted by a corresponding magnetic field of the magnetic coil of the first bearing portion, which results in a higher instability, a greater control complexity and a higher energy consumption.